In recent years, systems for monitoring networks have been used to maintain the quality of the networks. Such systems are called network monitoring systems. For example, there is a system in which a server is used to monitor an operating status of a plurality of transmission apparatuses on a network. The transmission apparatuses are apparatuses that are capable of transmitting data and voice and that are arranged in various places. Each of the transmission apparatuses is also capable of notifying the server of a network status among communication terminals via a base station. For example, each transmission apparatus transmits a notification message indicating whether a network is properly operating to the server. The server monitors the notification messages transmitted from the transmission apparatuses and provides a client with the network status. In this way, a user of the client grasps the network status.
In addition, there are network monitoring systems that employ hot-standby redundancy to increase their availability and reliability. Hot standby is a system multiplexing technique in which two systems having an identical configuration are arranged: one system (for example, an active system) is set in an active state and the other system (for example, a standby system) is set in a standby state while being caused to perform the same operation as that of the active system. Since both the active and standby systems monitor a network, even when a server in the active system malfunctions, a server in the standby system continuously monitors the network.
In addition, there has been proposed a technique for automatically migrating a system in which a violation of Service Level Agreement (SLA) could occur to an environment with availability. If a redundancy configuration is possible, a virtual machine operated on such risky system is migrated to two physical servers. If a redundancy configuration is not possible, a virtual machine operated on the risky system is migrated to a fault tolerant (FT) server. After a predetermined period of time elapses, if no risk is observed, the state that is before the redundancy configuration is created or the state that is before the virtual machine is migrated to the FT server is restored.
See, for example, Japanese Laid-open Patent Publication No. 2011-39740.
A server that belongs to a network monitoring system could be subjected to heavy load. One of such occasions is when a server receives a large number of notification messages (alarms) indicating that an abnormality has occurred from a transmission apparatus. Thus, such a server is provided with sufficient resource for processing such heavy load. Examples of the resource include resource of a processor and resource of a memory.
However, in a normal operation, namely, when the server is not under heavy load, the resource included in the server are not fully used. Therefore, in a system having a redundancy configuration, such as in a hot-standby system, a standby system may be provided with only the amount of resource that is sufficient for processing the load in a normal operation. In this way, the amount of resource used in the system is reduced.
However, if the amount of resource in the standby system is reduced, when an abnormality occurs in the monitoring performed in an active system and when the standby system is switched to serve as an active system, this system having been switched to newly serve as an active system will not withstand the heavy load. As a result, the reliability of the system is decreased.